Television system



Dec. 4, M PQNTE TELEVISION SYSTEM Filed Feb. 27. 1947 Patented Dec. 4, 1951 TELEVISION SYSTEM Maurice Ponte, Paris, France, assigner to Compagnic Generale de Telegrapliie Sans Fil, a corporation of France v Application February 27, 1947, Serial No. 731,275

In France February 9, 1946 Claims. (Cl. TIS-5,4)

In dealing with various problems, such as those arising in television, it is necessary to produce luminous energy at a point from a beam of particles in motion.v At present, these are generally electrons.

Such ris the case with tubes employed for television reception, whether the luminous image produced is observed directly or whether it is projected on to a screen.V

It is obviously necessary that the brightness given by the conversion of the image of the particles "should be as great as possible,- because the size of the images is limited by this character istic. In the art'as it is at present known, the cathodic fluoroscence of certain substances 'is employed, and much'research has been undertaken with the object of increasing the luminous output of this phenomenon,` both in connection with the nature of the screens upon which the beams impinge and in connection with the energy of the latter. However, in the latter connection, alimitation is set by the desire to produce a cathode spot of small dimensions, which imposes certain limits on the intensity conveyed by `the beam, so that it is necessary to employ very high acceleration voltages, sometimes ranging to about a hundred thousand volts. Under these conditions, 'it is diicult to produce suliciently stable fluorescent screens which do not burn'under the impact' of the electrons or which do not eventually change colour, which gives rise to modications of undesirable colour.

The present invention-concerns the means for providing astrong luminous screen,'the various points of-which canfollow the modulation of the exciting beam, while it provides a new solution of the problem of tubesffor the conversionv of kinetic energy into luminous energy, applied nonlimitatively to the reproduction of television images. To this end, the invention employs the luminous excitation of gases or of vapours traversed by beams of particles, and in particular by beams of electrons. I

yIt is known, especially since Coolidges experiments, that a beam of high-speed-electrons, P (Figure 1), obtained in any manner in the vacu- 4um tube T and traversing a thin impervious window F, produces in the air a luminous brush in 'the zone in which the electrons are stopped by the molecules of air at atmospheric pressure.

According to the invention, this phenomenon is utilised in a novel manner which will be clearly understood by reference to the accompanying non-limitative drawings, which are given to illustrate the following description, inwhch:

Figure 1 shows diagrannnatically ionization produced by passagev of electrons through a thin wall. v

Figure 2 shows a cathode ray tube constructed in accordance with this invention.

Figure 3 shows, partly in section, the development of parts constituting a resistance grid structure.

Figure 4 shows diierent structures for a goffered sheet in section. f

Figure 5 shows diagrammatically an arrangement of the plurality of gas chambers usedV in the production of different colors.

Figure 6' shows partly diagrammatically and partly in section a cathode ray tube involving 'a further feature of this invention.

The invention involves the idea of increasing the-pressure of the gas in order to localise the light emitted so as to determine a suillcientl'y small point to permit of a good deinition, in conjunction with improvements in the outlet Win dow rendering possible the' application of the principle and defining the mesh of the system.

To this end, a cathode tube C (Figure 2) comprises a very thin impervious windowfF. This tube may be constructed in the normal way, for example with tWoelectric lenses L1, Laand deiiecting systems illustrated as magnetic systems (MnMz). According to a known method' an image of a diaphragm defining the spot is producedat I, and the scanning systems permit of scanning a considerable fraction ci the window F, thus defining an electronic image which produces the luminous image transmitted, while the intensity of the beam is modulated, for example by the electrode W.

' According to the invention, a chamber V pro- 'Videdwith a light-transparent Iglass G is connected to the window F transparent to electrons. This chamber contains a gas which is illuminated at T under the action of the electrons assembled 4at I. 'It is necessary to localise this light to the f aluminum one-hundredth of a millimeter thick;

3 this light metal is relatively easy to obtain without pitting.

This window must have suicient dimensions to permit of obtaining an image with a good denition and at least with the substances at present known, this sheet could not withstand the pressure difference between the two containers C and V. According to the invention, this window is constructed with the aid of a resistant grid, the mesh l of which is illustrated in Figure 3a, the window 2 (section 3b) being stuck thereto or supported thereby. At 3c is shown the section ofan element of this cellular structure. One improvement consists in directing the sides of the mesh towards the region of rotation of the beam in the tube, so that the beam is not too greatly intercepted on the sides of the image.

The transparent sheet may thus consist of light material, either metallic or semi-insulating. The first category will include aluminium, for example, and the second will include sheets of plastic material, which can be obtained in very small thickness at least down to 100 a.

The grid itself may be ne if it is constructed from suitable metals such as high-resistance steel wires criss-crossing to form a mesh. The actual form of the grid may be either that of a squared pattern, or it may be limited to parallel wires.

Finally, the ensemble of the window and of its grid may be produced in a single operation by moulding, so as to obtain a goiered sheet, the depth of the meshes of which may be determined as a function of the pressure to be withstood. The goffering may also be formed on the two sides of the part transparent to electrons (Figures 4a and 4b). The moulding may be carried out on a metal grid, which gives a particularly resistant window. That part of the meshes c which faces towards the tube C may also be metallised so that its potential is well deiined, which is advantageous as compared with fluorescent screens acting by transparency. This construction aiiords the possibility of a Very fine mesh, having sides of the'order of T16 mm., so that a screen having sides of from several centimetres to one decimetre gives a suitable image.

It will be observed that the texture of the image may be given by the mesh of the window and that it will not be necessary to have too high a definition of the cathode spot, which affords the advantage of facilitating the construction of the tube.

The colour of the image is defined by the nature of the gas, and the apparatus according to the invention thus makes available to the person skilled in the art a very extensive range of colours as well as a screen which, by its very nature, is not liable to change colour or show fatigue.

The tubes according to the invention are therefore suitable not only for all applications in which it is desired to convert energy of particles into a luminous energy of one colour, but also for colour television. To this end, several tubes-for example three-one for each of the fundamental colours may be simultaneously employed by ,superposing their projections on a screen by means of suitable optical systems.

It is even possible to use a single cathode system exciting four gas chambers disposed, for example, as shown in Figure 5, which represents the complex tube s-een from the side of the face of the chambers. The mean position of the beam is determined by a polarisation of the deecting systems, which brings the scanning into the desired colour zone, each chamber giving the colour necessary for the superposition of the four colours to give a white. A four-lens projection system (not shown) ensures the superposed projection of the four coloured images on to a screen.

A tube of a given colour, constructed in accordance with the invention, can receive all necessary improvements on the cathode side. In

particular, in accordance with a known method,

in order to maintain a suitable scanning sensitivity in spite of the great speed of the electrons which is required, the scanning may be effected on slow electrons, for example 4,000 to 10,000 volts, and an additional acceleration to 100,000 or 500,000 volts will be effected by a combination of electric lenses. Figure 6 shows diagrammatically a tube according to the invention provided with this improvement.

This figure shows at K the emitting cathode, a rst electric system L1, L2 which gives by scanning through the elds M1 and M2 an intermediate image I1 owing to the modulation of the beam by the electrode W. The system V1, Vo gives the final image I2 on the window F after acceleration of the electrons to the desired voltage. The goffering of the window is shown on a scale much larger than the true scale in order to reproduce the structure described in Figure 4b. The voltage difference between Vo and K may be, for example, from 100,000 to 500,000 volts, the distribution of the voltages between the various electrodes being eiected according to the optical-requirements of the system. The gas chamber is illustrated at V, The inner face of the window will preferably be metallised on the thicker parts of the goi'fering so that the potential of the region of the final image may be well defined.

In the description of the invention the expression electronic has been employed, but it is understood that it is applicable to beams of othe charged particles.

I claim:

l. Television receiving tube comprising inside of an evacuated vessel an electron gun producing an electron beam, means for modulating said beam in intensity means for deecting the beam, means for impressing on the beam a high acceleration, said mentioned means being arranged in cascade at the beginning of the electron gun, a thin wall of material permeable to electrons closing tightly the said vessel, said wall being arranged within the sweep range of the' beam, a metallic grill or large mechanical resistance attached to said wall so as to render it more rigid, a chamber in part bounded by said wall and lled with gas under suitable pressure and a transparent wall closing said chamber through which the produced luminosity is observable.

2. Apparatus according to claim l, in which the wall permeable to electrons is made of aluminum.

3. Apparatus according to claim 1, in which the wall permeable to electrons is metallic.

4. Television receiving tube comprising inside of an evacuated vessel an electron gun producing an electron beam, means for modulating said "f beam in intensity, means for deecting the beam,

means for impressing on the beam a high acceleration, said mentioned means being arranged in cascade along the beam path at the beginning portion of the electron gun, a thin wall of material permeable to electrons closing tightly the said vessel, a metallic grill of large mechanical resistance located close to the said wall on the side opposite the beam impact, said wall being arranged within the sweep range of the beam, a chamber in part bounded by said wall and lled 5 with gas under pressure of over one atmosphere and a transparent Wall closing said chamber through which the produced luminosity is observable.

5. Apparatus according to claim 4, wherein the said wall consists of a thin sheet of molded material coating the said grill.

MAURICE PONTE.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Name Date Coolidge May 9, 1933 Number Number 

